CN110837109B - Atomic excited state spectrum obtaining method and hyperfine energy level measuring method and device - Google Patents
Atomic excited state spectrum obtaining method and hyperfine energy level measuring method and device Download PDFInfo
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- CN110837109B CN110837109B CN201911008172.2A CN201911008172A CN110837109B CN 110837109 B CN110837109 B CN 110837109B CN 201911008172 A CN201911008172 A CN 201911008172A CN 110837109 B CN110837109 B CN 110837109B
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Abstract
The invention belongs to the technical field of atomic spectra, and discloses a method for obtaining an atomic excited state spectrum, and a method and a device for measuring an atomic excited state hyperfine energy level structure by using the same. According to the method, first laser with frequency scanning and wavelength equal to transition wavelength of an atomic ground state-intermediate excited state is used as pump light, second laser with wavelength working at transition wavelength of the atomic intermediate excited state-higher excited state is used as probe light, and the pump light and the probe light are overlapped in an atomic glass bubble, so that a flat background optical double-resonance absorption spectrum is obtained. Meanwhile, a spectrum signal of ground state-intermediate excited state transition obtained in the process of pumping light frequency scanning is used as a frequency scale, and the hyperfine energy level structure of the atomic higher excited state is obtained by measuring the flat background optical double resonance absorption spectrum. The method has the advantages of simple device, flat background of the obtained atomic excited state spectrum, easy determination of the spectral line position and the like, and can be widely used for measuring the atomic excited state energy level structure.
Description
Technical Field
The invention belongs to the technical field of atomic spectra, and particularly relates to an atomic excitation state spectrum obtaining method and a hyperfine energy level measuring method and device.
Background
The understanding of the atomic level structure is essentially the acquisition, measurement and study of the "spectrum" associated therewith. The measurement of the atomic energy level structure can be used for making strict experimental inspection on various theoretical methods for calculating the hyperfine energy level structure, and has important significance in the aspects of quantum electrodynamics theoretical inspection, atomic frequency standard, laser separation same-digit, laser frequency stabilization and the like. Generally, atomic samples in a gas chamber at room temperature follow a maxwell-boltzmann distribution with atoms in random thermal motion and in a ground state energy level. Therefore, a single laser beam with the wavelength of the ground state-intermediate excited state transition passes through the atomic sample, the obtained spectrum submerges the spectral information of the hyperfine energy level transition between the atomic sample and the laser beam due to the Doppler broadening effect, and therefore technologies such as saturated absorption spectroscopy and polarization spectroscopy are developed to solve the problem. For the recognition of the higher excited state energy level structure of atoms, it is often necessary to obtain a spectrum of atomic intermediate excited state-higher excited state hyperfine energy level transitions. Because atoms at room temperature are in a ground state, the atoms of a specific velocity group are generally distributed to an intermediate excited state by laser light having a frequency resonant to the ground state-intermediate excited state; another laser is then swept between the intermediate and higher excited states at a frequency that produces a spectrum of transitions between the hyperfine energy levels of the two excited states.
At present, the common techniques for obtaining the atomic excited state spectrum are: optical dual resonance absorption spectroscopy, dual resonance optical pumping spectroscopy, and dual color polarization spectroscopy. Three types of stimuliCommon to the emission spectroscopy techniques is a laser (λ) resonant at a frequency in a ground-intermediate excited state1) Laser (lambda) of another wavelength to population atoms from the ground state to an intermediate excited state2) Frequency sweeping between an intermediate excited state-a higher excited state; the three spectra differ in that: the optical double resonance absorption spectrum is wavelength lambda2The laser is used as detection light to obtain an absorption spectrum signal of transition between an intermediate excited state and a higher excited state hyperfine energy level, and the absorption spectrum signal is used for the laser (lambda) with two wavelengths1、λ2) There is no requirement for polarization. The dichromatic polarization spectrum being the wavelength lambda1The circularly polarized laser is used as pump light to distribute atoms in an intermediate excited state and polarize the atoms, and the wavelength is lambda2The linear polarization laser is used as detection light, after the linear polarization laser passes through an atom sample, the linear polarization laser is divided into two beams by a half-wave plate and a cubic polarization beam splitter prism, and a bicolor polarization spectrum can be obtained by differential detection, and has definite requirements on the polarization of the two lasers. The optical double resonance absorption spectrum and the two-color polarization spectrum are both wavelengths lambda2The laser as the detection light causes uneven background of the two excited state spectra due to the nonlinear effect of the frequency scanning, and influences the signal-to-noise ratio of the spectra and the precise determination of the center position of the spectral line. Double resonance optical pumping spectrum, at wavelength λ1As both pump light and probe light, due to wavelength lambda2When the laser frequency is scanned between a pair of superfine energy level transitions of an intermediate excited state and a higher excited state, the population number of one superfine energy level of an atomic ground state is transferred to the other superfine energy level of the atomic ground state through a two-photon optical pumping effect, and the change of the population number is carried out by the wavelength lambda1The obtained spectrum still corresponds to the transition between the hyperfine energy levels of the atomic excited state, and the frequency of the spectrum is not scanned, so that the spectrum has a flat spectrum background, and the signal-to-noise ratio of the excited state spectrum is obviously improved. The three common excited state spectroscopy techniques, wavelength λ1And wavelength lambda2The lasers of all the devices operate in the same way and have the wavelength lambda1Is resonant to the transition line of the atomic ground state-intermediate excited state by scanning the wavelength lambda between the intermediate excited state and the higher excited state2OfThe frequency of the light is obtained, and therefore, a frequency scale must be established by auxiliary elements such as other additional optical elements, an acousto-optic modulator, an electro-optic modulator, a frequency comb, an optical cavity and the like, so as to measure the frequency interval between the higher excited hyperfine splitting energy levels of the atoms.
Based on an atomic ladder type energy level structure (a ground state, an intermediate excited state and a higher excited state), the traditional atomic excited state spectrum technology and measurement adopt the wavelength lambda1Is resonant to the transition line of the ground state to the intermediate excited state by scanning the wavelength lambda between the intermediate excited state and the higher excited state2Laser frequency is used for obtaining spectral information of the hyperfine splitting of the higher excited state, and then an additional optical element is used for establishing a frequency scale to complete the measurement of the hyperfine energy level structure of the atomic excited state. The above problems are two-fold, one is due to the lambda that is usually used as probe light2Laser frequency scanning causes uneven background of the obtained atomic excited state spectrum, and the central position of each spectral line is difficult to accurately determine; secondly, the operation mode of the laser for obtaining the atomic excitation state spectrum cannot directly obtain a frequency scale at the same time. Therefore, it is necessary to provide a novel atomic excited state spectrum and measurement technique to complete the measurement of the higher excited state hyperfine splitting frequency interval of atoms.
Disclosure of Invention
The invention overcomes the defects of the prior art, and solves the technical problems that: the atomic excited state spectrum method is simple in structure, flat in background and high in signal-to-noise ratio, and the method and the device for measuring the atomic excited state hyperfine energy level structure by using the atomic excited state spectrum method are provided.
In order to solve the technical problems, the invention adopts the technical scheme that: a method for obtaining an atomic excited state spectrum comprises the following steps: for wavelength lambda1Frequency scanning is carried out on first laser with the transition wavelength equal to the transition wavelength of the ground state-intermediate excited state of the atom, so that the first laser resonates one by one between superfine energy level transitions of the ground state-intermediate excited state of the atom, and the first laser is used as pumping laser; wavelength lambda of2Transition equal to intermediate-higher excited state of atomThe second laser with the wavelength is used as detection light and is incident to the atomic glass bubble, so that the second laser and atoms in the atomic glass bubble are subjected to detection after the second laser and the atoms in the atomic glass bubble act, the pumping laser and the detection light are reversely incident to the atomic glass bubble, and the pumping light and the detection light beam are overlapped; and then tuning the frequency of the detection light until the frequency is fixed after the flat background optical double-resonance absorption spectrum is obtained by detection.
The atom is an atomic system with a step-type energy level configuration of a ground state, an intermediate excited state and a higher excited state.
In addition, the invention also provides a method for measuring the hyperfine energy level structure of the atomic excited state, which comprises the following steps:
s1, wavelength λ1Frequency scanning is carried out on first laser with the transition wavelength equal to the transition wavelength of the ground state-intermediate excited state of the atom, the first laser resonates among superfine energy level transitions of the ground state-intermediate excited state of the atom, the first laser is divided into two parts, and one part of the first laser is incident to a ground state-intermediate excited state superfine transition spectrum device to obtain a spectrum signal of the superfine energy level of the intermediate excited state of the atom; the other part is used as pump laser;
s2, converting the wavelength lambda2A second laser with a transition wavelength equal to the transition wavelength of the intermediate excited state-higher excited state of the atom is emitted into the atomic glass bubble as a detection light, the detection light is enabled to be acted with the atom in the atomic glass bubble and then detected, the pumping laser beam is reversely emitted into the atomic glass bubble, and the pumping laser is overlapped with the detection light beam;
s3, tuning the frequency of the detection light until the frequency is fixed after the flat background optical double-resonance absorption spectrum is obtained through detection;
and S4, taking the spectrum signal of the hyperfine energy level of the intermediate excited state as a frequency scale, and measuring the flat background optical double resonance absorption spectrum to obtain the hyperfine energy level structure of the atom in the higher excited state.
The ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device, and the hyperfine energy level spectrum signal of the intermediate excited state is a saturated absorption spectrum signal without a Doppler background.
The step S3 specifically includes the following steps:
tuning the frequency of the probe light to obtain an optical double resonance absorption spectrum with a flat background, and analyzing and identifying hyperfine transition energy levels corresponding to spectral line peaks;
the step S4 specifically includes the following steps:
simultaneously recording a saturated absorption spectrum without a Doppler background and an optical double-resonance absorption spectrum with a flat background by using a digital oscilloscope; performing multimodal Lorentz fitting on the two spectral data, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectral data into a frequency axis; and calculating the frequency interval between the concerned spectral lines, namely the frequency interval of the hyperfine splitting of the higher excited state energy level.
Furthermore, the invention also provides a device for measuring the atomic excited state hyperfine energy level structure, which comprises an excited state spectrum obtaining unit and an excited state spectrum measuring unit;
the excited state spectrum measuring unit comprises a first laser, a first beam splitter and a ground state-intermediate excited state hyperfine transition spectrum device, wherein the first laser is used for emitting wavelength lambda1A first laser light equal to a transition wavelength of a ground state-intermediate excited state of an atom, and frequency-scanned between respective energy level transitions of the ground state to the intermediate excited state of the atom; the first laser is divided into two beams by a beam splitter, and one beam is incident to a ground state-intermediate excited state hyperfine transition spectrum device and is used for obtaining a hyperfine split spectrum signal of an intermediate excited state of an atom; the other beam is used as pumping light and is incident to the excited state spectrum obtaining unit;
the excited state spectrum obtaining unit comprises a second laser, an atomic glass bubble, a dichroic mirror and a detector, wherein the second laser is used for emitting wavelength lambda2The second laser is used as detection light and is incident to the atomic glass bubble, and then the detection light is detected by the detector after being separated from the pumping light by the dichroic mirror; the pumping light is incident to the atomic glass bubble after passing through the dichroic mirror and is in the atomic glass bubble with the probeAnd light metering is reversely superposed.
The ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device.
The saturated absorption spectrum device comprises a glass plate, a second atomic glass bubble, a half wave plate, a cubic polarization beam splitter prism, a second photoelectric detector, a third photoelectric detector, a first reflector and a second reflector, wherein a first laser is divided into two beams by a first beam splitter, one beam is incident to the glass plate and then divided into three beams of laser, two beams of laser reflected by front and rear optical surfaces of the glass plate are respectively used as reference light and detection light of the saturated absorption spectrum device, and the two beams of laser are respectively detected by the second photoelectric detector and the third photoelectric detector after passing through the second atomic glass bubble, the half wave plate and the cubic polarization beam splitter prism; one beam of laser transmitted through the glass plate is used as pump light in the saturated absorption spectrum device, and after being reflected by the first reflector, the second reflector and the cubic polarization beam splitter prism, the pump light and the probe light are reversely overlapped in the second atomic glass bubble through the half wave plate.
The beam splitter is formed by a half wave plate and a cubic polarization beam splitter prism.
The excited state spectrum measurement unit further comprises a calculation unit, wherein the calculation unit is used for carrying out multimodal Lorentz fitting on the spectrum data, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectrum data into a frequency axis; and calculating the frequency interval between the concerned spectral lines, namely the frequency interval of the hyperfine splitting of the higher excited state energy level.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention uses two beams of wave length as lambda1And λ2Is applied to atoms, wherein the wavelength lambda1As pump laser, frequency-swept between a ground state and an intermediate excited state, wavelength lambda2The laser is used as detection light, the frequency of the laser works between an intermediate excited state and a higher excited state (the frequency is not scanned), and the atomic intermediate excited state-higher excited state superfinishing is also obtained under the condition of not violating two-photon resonanceSpectral information of transitions between fine energy levels and due to probe light lambda2The frequency is not scanned, so that the excited state spectrum has a flat background, the signal to noise ratio of the excited state spectrum is improved, and the central position of the spectral line is easy to be precisely determined;
2. due to the pump light lambda1The frequency scanning of the method can obtain the spectrum of ground state-intermediate excited state hyperfine energy level transition by the common saturated absorption spectrum or polarization spectrum and other technologies while obtaining the spectrum of the atomic excited state spectrum with a flat background, namely, a frequency scale is established, and the unknown and higher excited state hyperfine splitting energy level structure is measured by atom-known intermediate excited state hyperfine splitting.
In a word, compared with the prior art, the device is simpler, and the excited state spectrum has the advantages of flat background, easy determination of the center position of the spectral line, high signal-to-noise ratio and convenient popularization.
Drawings
FIG. 1 shows cesium atoms 6S measured in an example of the present invention1/2-6P3/2-8S1/2(852nm +795nm) hyperfine energy level diagram;
fig. 2 is a schematic structural diagram of an apparatus for measuring an atomic excited state hyperfine energy level structure according to an embodiment of the present invention;
FIG. 3 shows an optical double resonance absorption spectrum and a saturated absorption spectrum with a flat background measured according to an embodiment of the present invention; in the figure, curves L1-L4 are respectively an optical double resonance absorption spectrum with a flat background, a saturated absorption spectrum without a Doppler background, a saturated absorption spectrum with a Doppler background and an absorption spectrum with Doppler broadening;
FIG. 4 is a schematic diagram of a multi-peak Lorentz fit of a saturated absorption spectrum without a Doppler background obtained in an embodiment of the present invention;
FIG. 5 is a graph of a multi-peak Lorentz fit of a flat background optical double resonance absorption spectrum obtained with an embodiment of the present invention, and a saturated absorption spectrum as a "frequency scale";
fig. 6 is a diagram illustrating a conventional optical double resonance absorption spectrum in the prior art.
In the figure: the device comprises a 1-852nm semiconductor laser, a 2-852nm optical isolator, a 3-852nm half wave plate, a 4-cubic polarization beam splitter prism, a glass plate with the thickness of 5-10 mm, a 6-cesium bulb, a 7-852nm half wave plate, an 8-cubic polarization beam splitter prism, a 9-photoelectric detector, a 10-photoelectric detector, an 11-reflector, a 12-reflector and a 13-reflector; 14-795nm semiconductor laser, 15-795nm optical isolator, 16-795nm half wave plate, 17-cubic polarization beam splitter prism, 18-cesium bulb, 19-795nm/852nm dichroic mirror and 20-photoelectric detector.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments; all other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a method for measuring an atom excited state hyperfine energy level structure, which changes the operation mode of two lasers, namely wavelength lambda1As pump laser, frequency-swept between a ground state and an intermediate excited state, wavelength lambda2The laser as the detection light has the frequency working between the intermediate excitation state and the higher excitation state (the frequency is not scanned), and the spectral information of the transition between the atomic intermediate excitation state and the hyperfine energy level of the higher excitation state is obtained under the condition of not violating the two-photon resonance, and the detection light lambda is used2The frequency is not scanned, so that the excited state spectrum has a flat background, the signal to noise ratio of the excited state spectrum is improved, and the central position of a spectral line is easy to determine; and due to the pump light lambda1The frequency scanning of the method can obtain the spectrum of the ground state-intermediate excited state hyperfine energy level transition through a common saturated absorption spectrum or a polarization spectrum technology while obtaining the spectrum of the atomic excited state, namely, a frequency scale is established, and an unknown and higher excited state hyperfine splitting energy level structure is measured by the known hyperfine splitting of atoms. In particular, the test of the embodiments of the present inventionThe method comprises the following steps:
s1, wavelength λ1Frequency scanning is carried out on first laser with the transition wavelength equal to that of the ground state-intermediate excited state of the atom, the first laser resonates among the hyperfine energy levels of the ground state-intermediate excited state of the atom, the first laser is divided into two parts, and one part of the first laser is incident to a ground state-intermediate excited state hyperfine transition spectrum device to obtain a spectrum signal of hyperfine energy level splitting of the intermediate excited state of the atom; the other part is used as pump laser;
s2, converting the wavelength lambda2Detecting after the second laser light with the transition wavelength equal to the intermediate excited state-higher excited state of the atom is incident to the atom in the cesium bubble as detection light, and reversely incident the pump light beam and the detection light beam to the atom in the cesium bubble and overlapping the pump light beam and the detection light beam;
s3, tuning the frequency of the detection light until the optical double resonance absorption spectrum of the flat background is obtained by detection;
and S4, taking the hyperfine transition spectrum signal of the intermediate excited state as a frequency scale, and measuring the flat background optical double resonance absorption spectrum to obtain the hyperfine energy level structure of the atom in the higher excited state.
Specifically, the method for measuring the hyperfine energy level structure of the atomic excited state provided by the embodiment of the invention is suitable for an atomic system with a ladder type energy level configuration of a ground state, an intermediate excited state and a higher excited state.
Specifically, in this embodiment, the ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device, and the spectrum signal of the hyperfine energy level of the intermediate excited state is a saturated absorption spectrum signal with a doppler background removed.
Specifically, in this embodiment, the step S3 specifically includes the following steps: tuning the wavelength of the detection light to obtain an optical double resonance absorption spectrum with a flat background, and analyzing and identifying hyperfine transition energy levels corresponding to spectral line peaks;
the step S4 specifically includes the following steps: simultaneously recording a background-free saturated absorption spectrum and an optical double-resonance absorption spectrum with a flat background by using a digital oscilloscope; performing multimodal Lorentz fitting on the two spectral data, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectral data into a frequency axis; and calculating the frequency interval between the concerned spectral lines, namely the frequency interval of the hyperfine splitting of the higher excited state energy level.
The embodiment of the invention also provides a device for measuring the hyperfine energy level structure of the atomic excited state, and the device can be used for measuring the hyperfine energy level of the cesium atomic excited state. Fig. 1 is a diagram showing an energy level structure of cesium atoms, and fig. 2 is a schematic structural diagram showing a device for measuring an excited-state hyperfine energy level structure of atoms according to an embodiment of the present invention, where the device includes an excited-state spectrum obtaining unit and an excited-state spectrum measuring unit. The excited state spectrum obtaining unit is used for obtaining spectral information of hyperfine splitting of atoms with higher excited state energy levels through experiments; the excited state spectrum measuring unit is used for realizing the establishment of a frequency scale, measuring the frequency interval of the hyperfine splitting of higher excited state energy level and processing related computer software data.
As shown in FIG. 2, the excited state spectrum measuring unit comprises a 852nm semiconductor laser 1, an isolator 2, a beam splitter formed by a half wave plate 3 and a cubic polarization beam splitter 4, and a ground state-intermediate excited state hyperfine transition spectrum device, wherein the first laser 1 is used for emitting a wavelength lambda1First laser light of transition wavelength equal to ground state-intermediate excited state of atom, i.e. 6S of cesium atom1/2-6P3/2And the first laser light performs frequency scanning between the respective energy level transitions from the ground state of the atom to the intermediate excited state; the first laser is incident to the ground state-intermediate excited state hyperfine transition spectrum device through the light reflected by the cubic polarization beam splitter prism 4, and is used for obtaining a hyperfine split spectrum signal of the intermediate excited state of the atom, namely a frequency scale; the light transmitted through the cubic polarization beam splitter prism 4 is incident to the excited state spectrum obtaining unit as pump light.
Wherein the ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device, and the saturated absorption spectrum device comprises a glass plate 5 and a cesium bulb 6The first laser is divided into two beams by the first beam splitter, one beam is incident to the glass plate 5 and then divided into three beams of laser, the two beams of laser reflected by the front and rear optical surfaces of the glass plate 5 are respectively used as reference light and detection light of the saturated absorption spectrum device, and the two beams of laser are respectively detected by the second photoelectric detector 9 and the third photoelectric detector 10 after passing through the cesium bulb 6, the half-wave plate 7 and the cubic polarization beam splitter prism 8; one beam of laser transmitted through the glass plate 5 is used as pump light in a saturated absorption spectrum device, is reflected by the first reflecting mirror 11, the second reflecting mirror 12 and the cubic polarization beam splitting prism 8, and then is reversely overlapped with detection light in the cesium bulb 6 through the half wave plate 7. The saturated absorption spectrum signal containing Doppler background is obtained at the detector 9, the absorption spectrum signal of Doppler broadening background of the reference light obtained at the detector 10 after passing through the cesium bulb 6 is obtained, the difference between the two spectrum signals is the saturated absorption spectrum signal without background, and as shown in fig. 3, the saturated absorption spectrum signal is used as a frequency scale to measure 8S in a higher excited state1/2Hyperfine splitting of energy levels.
As shown in fig. 2, the excited state spectrum obtaining unit includes a 795nm semiconductor laser 14, a cesium bulb 18, a dichroic mirror 19, and a photodetector 20, and the second laser 14 is configured to emit light having a wavelength λ2Is equal to atom 6P3/2-8S1/2Second laser light between transition lines with wavelength lambda2After passing through an isolator 15, a half-wave plate 16 and a cubic polarization beam splitter prism 17, the second laser light enters a cesium bubble 18 as detection light, and then is detected by the photodetector 20 after passing through a dichroic mirror 19; the pumping light is incident to the cesium bubbles 18 after passing through the dichroic mirror 19 and is reversely overlapped with the detection light in the cesium bubbles 18. Because the detection light only works at 6P3/2-8S1/2Between the transition lines, the frequency is not scanned, so an optical double resonance absorption spectrum with a flat background will be obtained at the photodetector 20, typical experimental results are shown in fig. 3.
In this embodiment, the wavelength λ1852.356nm laser as pump light with frequency of cesium atom 6S1/2F＝4-6P3/2Scanning between transition lines of 3, 4 and 5 for 6S1/2-6P3/2Is Δ as a frequency detuning of a pair of hyperfine transition lines1(ii) a Wavelength lambda2794.608nm laser as probe light with frequency of 6P3/2-8S1/2At a position between the transition lines of (2), relative to 6P3/2-8S1/2Is Δ as a frequency detuning of a pair of hyperfine transition lines2. The Gaussian diameters of the detection beam and the pumping beam are approximately equal to 1mm, and the laser powers are equal<About.1 mW, both are superposed in the cesium bubbles at room temperature in reverse by means of a dichroic mirror (cesium bubbles are cylindrical in shape, length about 70mm, diameter about 25 mm). After considering Doppler effect, delta under the condition of satisfying two-photon resonance1+Δ2+(v/λ1-v/λ2) 0(v is the velocity component of atomic motion along the path of the speed of light), probe light λ2After passing through the cesium bubble, the optical double resonance absorption spectrum of the atomic excited state with a flat background can be obtained by detecting the cesium bubble at the photodetector 20.
When the above-mentioned background-flat atomic excited state optical double resonance absorption spectrum is obtained, the spectrum is obtained due to lambda1The frequency of pump light is 852.356nm at cesium atom 6S1/2F＝4-6P3/2F' is a manner of scanning between transition lines of 3, 4, 5, and thus 6S can be obtained by a saturated absorption spectroscopy technique (or a polarization spectroscopy technique)1/2-6P3/2Ultra-fine transition spectral signals, the interval between spectral lines is completely formed by the intermediate excited state 6P3/2Hyperfine splitting frequency interval determination of energy levels, 6P3/2The state energy level corresponds to a cesium atom D2 line, the hyperfine frequency interval of the energy level splitting is accurately determined (see figure 1), so the hyperfine transition spectrum can be used as a frequency scale for measuring the structure of the higher excited state energy level, and the higher excited state 8S is completed1/2And (5) measuring the hyperfine energy level structure. Therefore, the invention is characterized in that: at a wavelength λ1Under the scanning mode of 852.356nm laser frequency, excited state 6P is obtained simultaneously3/2、8S1/2And (4) spectrum information of hyperfine splitting of energy level.
Passing the detection signals of the photodetectors 9, 10 and 20 through an oscillographThe horizontal axis of the saturation absorption spectrum without background and the optical double resonance absorption spectrum with flat background recorded by the oscilloscope is time, and the vertical axis of the saturation absorption spectrum without background and the optical double resonance absorption spectrum with flat background represent the magnitude of the amplitude of the hyperfine transition spectrum signal. Importing background-free saturated absorption spectrum data into Origin software for drawing, performing multi-peak Lorentz fitting on a saturated absorption spectrum curve, determining a time point corresponding to the center of each hyperfine transition spectral line (see figure 4), calculating delta t according to the time interval between a pair of hyperfine transition spectral lines, and calculating the frequency interval between the pair of hyperfine transition spectral lines from an intermediate excited state 6P3/2The size of the hyperfine splitting of the energy level (known, see fig. 1) gives Δ ν852Then the frequency interval Deltav corresponding to the unit time can be obtained852And/Δ t, from which the time axis of the saturated absorption spectrum is linearly converted into the frequency axis.
Because the saturated absorption spectrum without background and the optical double-resonance absorption spectrum with flat background are both at the wavelength lambda1Obtained simultaneously when scanning at 852.356nm laser frequency, likewise with Δ ν852The method comprises the steps of firstly, linearly converting a time axis of an optical double-resonance spectrum signal with a flat background into a frequency axis by a/delta t value, then carrying out multimodal Lorentz fitting on the optical double-resonance spectrum signal with the flat background by Origin software, determining a frequency value corresponding to the center of each hyperfine transition spectrum line, and calculating a frequency interval delta v between the hyperfine transition spectrum lines852' (see FIG. 5). As shown in fig. 5, the embodiment of the present invention obtains an optical double resonance absorption spectrum with a flat background; as shown in fig. 6, which is a schematic diagram of a conventional optical dual-resonance absorption spectrum obtained by measurement in the prior art, the background of the spectrum is extremely uneven, and it can be seen from the diagram that the signal-to-noise ratio of the spectrum obtained by the present invention is greatly improved, and the accuracy of energy level measurement can be improved.
Because of the detection light wavelength lambda in the excitation state spectrum experiment2794.608nm, and the frequency scale is based on λ1Established when scanning laser frequency of 852.356nm, the frequency interval Deltav852’*λ1/λ2＝Δν795The frequency interval value corresponding to the hyperfine splitting of the higher excited state energy level of the atom (because the laser Doppler shift of the atom with the same speed to different wavelengths does not existIn the same way, all optical double resonance absorption lines satisfy the two-photon resonance condition delta1+Δ2+(v/λ1-v/λ2) 0). According to the data processing flow and method, the excited state 8S is finally obtained1/2F″＝3-8S1/2The hyperfine frequency separation between F ″ ═ 4 was 875.44MHz, consistent with the results reported in the literature, see fig. 1.
Taking cesium atoms as an example, the embodiment of the invention provides a method for measuring an atomic excited state hyperfine energy level structure, which comprises the following steps:
(1) tuning pump light frequency with wavelength of 852nm to cesium atom 6S1/2F＝4-6P3/2Scanning the frequency of the transition line F' ═ 3, 4 and 5 to obtain a corresponding background-free saturated absorption spectrum, and establishing a frequency scale according to the signal;
(2) tuning the detection light with 795nm wavelength to obtain optical double resonance absorption spectrum with flat background, and analyzing and identifying the atomic excited state 6P corresponding to each spectral line3/2-8S1/2Which pair of hyperfine transition levels in the transition;
(3) a digital oscilloscope is used for simultaneously recording a background-free saturated absorption spectrum (a frequency scale) and an optical double resonance absorption spectrum (an atomic excitation state hyperfine transition spectrum) with a flat background, and the figure is shown in figure 3;
(4) carrying out multimodal Lorentz fitting on the two spectral data by Origin software, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectral data into a frequency axis;
(5) the frequency separation between the spectral lines of interest, i.e. the higher excited state 8S, is calculated1/2F ″ -3/4-level hyperfine splitting frequency interval;
above is the excited state 8S of cesium atom1/2Hyperfine level splitting measurements are an example, and the above method is equally applicable to measurements of other atomic excited state level structures.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method for obtaining an atomic excited state spectrum is characterized by comprising the following steps: for wavelength lambda1Frequency scanning is carried out on first laser with the transition wavelength equal to the transition wavelength of the ground state-intermediate excited state of the atom, so that the first laser resonates among superfine energy level transitions of the ground state-intermediate excited state of the atom and is used as pumping laser; wavelength lambda of2The second laser with the transition wavelength equal to the transition wavelength of the intermediate excited state-higher excited state of the atom is used as detection light to be emitted to the atomic glass bubble, the light intensity of the detection light which is acted with the atom in the atomic glass bubble is directly detected through a single detector, the pump laser and the detection light are reversely emitted to the atomic glass bubble, and the pump laser and the detection light beam are overlapped; and then tuning the frequency of the detection light until the frequency is fixed after the flat background optical double-resonance absorption spectrum is obtained by detection.
2. The method for obtaining an atomic excited state spectrum according to claim 1, wherein the atom is an atomic system having a step-like energy level configuration of a ground state, an intermediate excited state, and a higher excited state.
3. A method for measuring an atomic excited state hyperfine energy level structure is characterized by comprising the following steps:
s1, wavelength λ1Frequency scanning is carried out on first laser with the transition wavelength equal to the transition wavelength of the ground state-intermediate excited state of the atom, the first laser resonates among superfine energy level transitions of the ground state-intermediate excited state of the atom, the first laser is divided into two parts, and one part of the first laser is incident to a ground state-intermediate excited state superfine transition spectrum device to obtain a spectrum signal of superfine energy level splitting of the intermediate excited state of the atom; another partAs pump laser light;
s2, converting the wavelength lambda2A second laser with a transition wavelength equal to the transition wavelength of the intermediate excited state-higher excited state of the atom is emitted into the atomic glass bubble as a detection light, the detection light is enabled to be acted with the atom in the atomic glass bubble and then detected, the pumping laser beam is reversely emitted into the atomic glass bubble, and the pumping laser is overlapped with the detection light beam;
s3, tuning the frequency of the detection light until the frequency is fixed after the flat background optical double-resonance absorption spectrum is obtained through detection;
and S4, taking the spectrum signal of the hyperfine energy level of the intermediate excited state as a frequency scale, and measuring the flat background optical double resonance absorption spectrum to obtain the hyperfine energy level structure of the atom in the higher excited state.
4. The method for measuring the hyperfine energy level structure of the atomic excited state according to claim 3, wherein the ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device, and the spectrum signal of the hyperfine energy level of the intermediate excited state is a saturated absorption spectrum signal without Doppler background.
5. The method for measuring the atomic excited state hyperfine energy level structure according to claim 4, wherein the step S3 specifically comprises the following steps:
tuning the frequency of the probe light to obtain an optical double resonance absorption spectrum with a flat background, and analyzing and identifying hyperfine transition energy levels corresponding to spectral line peaks;
the step S4 specifically includes the following steps:
simultaneously recording a saturated absorption spectrum without a Doppler background and an optical double-resonance absorption spectrum with a flat background by using a digital oscilloscope; performing multimodal Lorentz fitting on the two spectral data, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectral data into a frequency axis; and calculating the frequency interval between the concerned spectral lines, namely the frequency interval of the hyperfine splitting of the higher excited state energy level.
6. An apparatus for measuring an atomic excited state hyperfine energy level structure, characterized by being used for implementing the method for measuring an atomic excited state hyperfine energy level structure according to claim 3, and comprising an excited state spectrum obtaining unit and an excited state spectrum measuring unit;
the excited state spectrum measuring unit comprises a first laser (1), a first beam splitter and a ground state-intermediate excited state hyperfine transition spectrum device, wherein the first laser (1) is used for emitting wavelength lambda1A first laser light equal to a transition wavelength of a ground state-intermediate excited state of an atom, and frequency-scanned between respective energy level transitions of the ground state to the intermediate excited state of the atom; the first laser is divided into two beams by a beam splitter, and one beam is incident to a ground state-intermediate excited state hyperfine transition spectrum device and is used for obtaining a hyperfine split spectrum signal of an intermediate excited state energy level of an atom; the other beam is used as pumping light and is incident to the excited state spectrum obtaining unit;
the excited state spectrum obtaining unit comprises a second laser (14), an atomic glass bubble (18), a dichroic mirror (19) and a first photodetector (20), wherein the second laser (14) is used for emitting wavelength lambda2A second laser having a transition wavelength equal to the transition wavelength of the intermediate excited state to the higher excited state of the atom, said second laser being incident as a detection light to the atomic glass bubble (18), and then being detected by said first photodetector (20) after being separated from the pump light by the dichroic mirror (19); the pumping light is incident to the atomic glass bubble (18) after passing through the dichroic mirror (19), and is reversely superposed with the detection light in the atomic glass bubble (18); the excited state spectrum measurement unit further comprises a calculation unit, wherein the calculation unit is used for carrying out multimodal Lorentz fitting on the spectrum data, determining the central position of each hyperfine transition spectral line, and linearly converting the time axis of the spectrum data into a frequency axis; and calculating the frequency interval between the concerned spectral lines, namely the frequency interval of the hyperfine splitting of the higher excited state energy level.
7. The device for measuring the hyperfine energy level structure of the atomic excited state according to claim 6, wherein the ground state-intermediate excited state hyperfine transition spectrum device is a saturated absorption spectrum device.
8. The apparatus for measuring the hyperfine energy level structure of an atomic excited state according to claim 7, the device is characterized by comprising a glass plate (5), a second atomic glass bubble (6), a half-wave plate (7), a cubic polarization beam splitter prism (8), a second photoelectric detector (9), a third photoelectric detector (10), a first reflector (11) and a second reflector (12), the first laser is divided into two beams by the first beam splitter, one beam is incident to the glass plate (5) and then divided into three beams, two beams of laser reflected by two optical surfaces in front of and behind the glass plate (5) are respectively used as reference light and detection light of the saturated absorption spectrum device, and the reference light and the detection light are respectively detected by a second photoelectric detector (9) and a third photoelectric detector (10) after passing through a second atomic glass bubble (6), a half-wave plate (7) and a cubic polarization beam splitter prism (8); one beam of laser transmitted by the glass plate (5) is used as pumping light in a saturated absorption spectrum device, is reflected by the first reflecting mirror (11), the second reflecting mirror (12) and the cubic polarization beam splitter prism (8), and then is reversely overlapped with detection light in the second atomic glass bubble (6) through the half wave plate (7).
9. The apparatus for measuring the hyperfine energy level structure in the atomic excited state according to claim 6, wherein the beam splitter is formed by a half-wave plate and a cubic polarization beam splitter prism.
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